CMP is often utilized for planarizing semiconductor wafer surfaces in the fabrication of integrated circuits. Such CMP processes typically involve rubbing the surface of the wafer against a polishing device to remove high spots on the wafer surface. The wafer is held in a stationary or rotating fixture while being pressed against a stationary or rotating polishing pad. Generally, at least one of the pad and the arm are moving with respect to each other to create friction between the pad and wafer for polishing the wafer. The polishing pad is supported on a platen which may be rotated during the CMP process. The polishing surface of the polishing pad may be constructed from a variety of materials, such as open-cell foam polyurethane or a sheet of polyurethane with a grooved surface. The polishing surface is relatively rough in comparison to the semiconductor wafer surface. A slurry of polishing fluid is often introduced to further aid in the CMP process.
The surface of the polishing pad gradually becomes glazed due to the accumulation of material removed during the polishing process. Accordingly, the pad must be periodically conditioned to restore its rough surface texture. Such conditioning involves the application of an abrasive surface of a conditioning device against the surface of the polishing pad to remove the accumulated debris, and it may remove a portion of the polishing pad surface itself. Conditioning will expose a renewed polishing pad surface having characteristics essentially the same as or similar to a new pad. Commonly, a polishing pad is conditioned after each semiconductor wafer is polished.
Several types of conditioning devices are known in the art, for example a conditioning disk having a diamond abrasive surface formed thereon. The abrasive surface is rubbed against the polishing pad surface at a predetermined velocity, for a predetermined length of time, with a predetermined amount of force exerted between. The abrasive diamond surface functions to condition or roughen the surface of the polishing pad. The amount of conditioning may be varied by changing the velocity, time of contact, or force between the conditioning device and the polishing pad. For instance, the amount of conditioning will increase with an increased velocity, a lengthened time period, or an increased force between the two surfaces.
Too much or too little conditioning will provide undesirable results. CMP specifications are tightening as the semiconductor industry progresses to manufacturing semiconductor wafers at smaller technology nodes, such as 22 nm and 14 nm nodes. Polish pad resurfacing and preparation processes, such as slurry distribution, are being developed for manufacturing at smaller technology nodes and 450 mm wafers. Controlled conditioning of a polish pad in CMP is commonly utilized to create more consistent polish conditions throughout a CMP usability lifetime of a polish pad.
Current polish pad resurfacing and preparation processes have several limitations and drawbacks. One limitation is that a polish pad is often not prepared and/or resurfaced consistently over the whole surface of the pad. For example, a polish pad is often conditioned utilizing a rotating conditioning disc on a conditioning arm moving at differential sweeping motions and speeds to resurface the polish pad. The sweep speed is often zero at points where the sweeping motion is reversed. Alternatively, it may be elevated at other locations of a sweeping motion, such as at a periphery of a “donut” hole at the center of an orbital sweeping motion. The differential sweeping motions and speeds commonly result in differential removal rates of the unconditioned pad at turning points of the sweeping motion and at areas of the pad conditioned at higher sweeping speeds.
Another limitation is that conditioning arms currently utilized in polish pad resurfacing and preparation processes often do not provide for control or measurement of dynamic or differential downward forces applied to the polish pad through the arms. Instead, downward forces that are unitary and static in nature are commonly applied through the arms via a pneumatic system. Often the unitary static downward forces applied through the arms are difficult to measure, such as by utilizing a load cell.
Another limitation is that arms currently utilized in polish pad resurfacing and preparation processes, such as a conditioning arm, are often mechanically unstable due to the high wearing out of bearings and other mechanical parts associated with moving the arms. Another limitation is that separate mechanical parts are required for pad conditioning and pad cleaning. A conditioning arm generally has no cleaning capability for cleaning a polish pad. Similarly, a cleaning arm or other means for cleaning a polish pad, such as an atomizer, generally has no pad conditioning capability.
A need therefore exists for methodology enabling (1) consistent preparation and/or resurfacing over a whole surface of a polish pad in a CMP tool, (2) control and/or measurement of dynamic and/or differential downward forces applied to a polish pad in a CMP tool, (3) mechanical stability regarding mechanical parts utilized in a CMP tool and (4) a reduction in the number of separate mechanical parts in a CMP tool utilized for preparing and/or resurfacing a polish pad in a CMP process, and an apparatus therefore.